The present invention relates to a liquid-vapor contact device for contacting liquid and vapor phases of a mixture in, for example, a distillation column. More particularly, the present invention relates to such a liquid-vapor contact device including a perforate plate-like body for effecting the contact between the liquid and vapor phases. Even more particularly the present invention relates to such a liquid-vapor contact device having flow deflectors for imparting momentum to the vapor phase and thereby the liquid phase and flow impedance members for impeding the flow of the liquid phase. Still even more particularly the present invention relates to such a device in which the flow impedance members are formed on a plurality of elongated members overlying the plate-like body and in which the elongated members provide side surfaces for liquid film to form from the liquid phase of the mixture.
In the chemical arts, multi-component mixtures are rectified in distillation columns having liquid-vapor contact devices to contact ascending vapor and descending liquid phases of the multi-component mixture. Through such contact, the descending liquid phase becomes ever more concentrated in the heavier components of the mixture to be separated while the ascending vapor phase becomes every more concentrated in the lighter components of the mixture.
Common liquid-vapor contact devices are known as bubble cap plates and sieve trays. In both types of devices the vapor phase ascends through openings provided in the trays or plates to contact liquid of the liquid phase traversing the trays or plates. The liquid phase is supplied to and is discharged from inlet and outlet sections of the plates or trays by downcomers provided in the column. In such manner, the vapor bubbles up through the liquid and mixes with the liquid to effect a change in the composition of the liquid and the vapor. Thereafter, the liquid is discharged from a particular plate or tray and the vapor ascends from the liquid to the next succeeding plate or tray.
Another type of liquid-vapor contact element is a packing. In a packing, the liquid phase of the mixture descends as a film formed on the packing elements while the vapor rises through interstices between packing elements. A common packing element is structured packing in which vertically oriented sheets are provided with crimps which criss-cross each other as between sheets. Structured packings have found widespread use in the petrochemical and air separation industry due to their low pressure drop characteristics which can be translated into power savings and increased separations of mixtures which are by nature are difficult to separate. The disadvantage of structured packing has been one of cost when compared to trays or plates.
In order to improve the performance of a tray-like element, a liquid-vapor contact device has been proposed in U.S. Pat. No. 5,091,119 (hereby incorporated by reference as if fully set forth herein). This liquid vapor contact element of this patent has a tray formed of expanded metal. The tray is provided with slit like openings and tongue-like elements associated with the openings to propel ascending vapor in a direction taken from an inlet to an outlet section of the tray. In order to increase the residence time of the liquid, an overlying expanded metal grid work is provided to inhibit the flow of the liquid from the inlet to the outlet.
As will be discussed, the present invention provides an improved liquid-vapor contact element in the form of a tray that incorporates features of U.S. Pat. No. 5,091,119, with features of structured packing by providing surfaces on which descending liquid films can be formed to enhance the area of liquid-vapor contact.